318 exhaust valve differences

[Duodec]

Melling and other mfgrs show one exhaust valve for early 318s up to 1978, then a different part number for 1979 to the end of LA production.  They're identical specs except the early valve is 5.003" OAL and the later one is 4.982" OAL.  The year of change doesn't match up with the move to hydraulic roller cam.

Any idea why the change?  I had thought the valve train on the 318 stayed pretty much constant through the years.

Melling p/n 1971 exhaust valve  V1329   and 1978 and later V1399

Thanks
Rich

[Duodec]

I think my task on these forums will be to ask the unanswerable questions...   

[Burdar]

Didn't later model engines get exhaust valve rotators?  That may have necessitated a valve change.

[Duodec]

Thanks!  That may be the case.  Apparently early on some 'heavy duty truck' application 318s got rotators.  But there's notes about a late '80s 318 Gran Fury junkyard engine having exhaust rotators.  Unless all of the 318s from '79 on had rotators (not just trucks) not sure why that shorter valve would be listed for cars as well as trucks from that date on.  And Rock Auto does list some other brand valves with the shorter OAL and the note about valve rotators on heavier vans and trucks in the late 80s until Magnums took over.

But that's good enough info for me.  I should be able to use the early valves that I already have on the 302 heads without rotators, and look for another set if ever needed.

Any preference currently for good brands for stock valves?  Melling are still made in North America, Sealed Power manufacture appears to be all over the place, no way to tell without seeing the box before you buy.  The sets I have now are Melling exhaust and Inland intakes